Reproducibility of haptic waveform

ABSTRACT

A system may include an electromagnetic load capable of generating a haptic event and a haptic processor configured to receive at least one first parameter indicative of a desired perception of the haptic event to a user of a device comprising the electromagnetic load, receive at least one second parameter indicative of one or more characteristics of the device, and process the at least one first parameter and the at least one second parameter to generate a driving signal to the electromagnetic load in order to produce the desired perception to the user despite variances in the device that cause an actual perception of the haptic event to vary from the desired perception.

CROSS-REFERENCES AND RELATED APPLICATION

The present disclosure claims benefit of U.S. Provisional Patent Application Ser. No. 62/925,307, filed Oct. 24, 2019, which is incorporated by reference herein in its entirety.

FIELD OF DISCLOSURE

The present disclosure relates in general to methods, apparatuses, or implementations for haptic devices. Embodiments set forth herein may disclose improvements to how haptic events are created, specified, and stored.

BACKGROUND

Vibro-haptic transducers, for example linear resonant actuators (LRAs), are widely used in portable devices such as mobile phones to generate vibrational feedback to a user. Vibro-haptic feedback in various forms creates different feelings of touch to a user's skin and may play increasing roles in human-machine interactions for modern devices.

An LRA may be modelled as a mass-spring electro-mechanical vibration system. When driven with appropriately designed or controlled driving signals, an LRA may generate certain desired forms of vibrations. For example, a sharp and clear-cut vibration pattern on a user's finger may be used to create a sensation that mimics a mechanical button click. This clear-cut vibration may then be used as a virtual switch to replace mechanical buttons.

FIG. 1 illustrates an example of a vibro-haptic system in a device 100. Device 100 may comprise a controller 101 configured to control a signal applied to an amplifier 102. Amplifier 102 may then drive a vibrational actuator (e.g., haptic transducer) 103 based on the signal. Controller 101 may be triggered by a trigger to output to the signal. The trigger may, for example, comprise a pressure or force sensor on a screen or virtual button of device 100.

Among the various forms of vibro-haptic feedback, tonal vibrations of sustained duration may play an important role to notify the user of the device of certain predefined events, such as incoming calls or messages, emergency alerts, and timer warnings, etc. In order to generate tonal vibration notifications efficiently, it may be desirable to operate the haptic actuator at its resonance frequency.

The resonance frequency f₀ of a haptic transducer may be approximately estimated as:

$\begin{matrix} {f_{0} = \frac{1}{2\pi\sqrt{CM}}} & (1) \end{matrix}$ where C is the compliance of the spring system, and M is the equivalent moving mass, which may be determined based on both the actual moving part in the haptic transducer and the mass of the portable device holding the haptic transducer.

Due to sample-to-sample variations in individual haptic transducers, mobile device assembly variations, temporal component changes caused by aging, and use conditions such as various different strengths of a user gripping of the device, the vibration resonance of the haptic transducer may vary from time to time.

FIG. 2 illustrates an example of a linear resonant actuator (LRA) modelled as a linear system. LRAs are non-linear components that may behave differently depending on, for example, the voltage levels applied, the operating temperature, and the frequency of operation. However, these components may be modelled as linear components within certain conditions. In this example, the LRA is modelled as a third order system having electrical and mechanical elements. In particular, Re and Le are the DC resistance and coil inductance of the coil-magnet system, respectively; and Bl is the magnetic force factor of the coil. The driving amplifier outputs the voltage waveform V(t) with the output impedance Ro. The terminal voltage V_(T)(t) may be sensed across the terminals of the haptic transducer. The mass-spring system 201 moves with velocity u(t).

A haptic system may require precise control of movements of the haptic transducer. Such control may rely on the magnetic force factor Bl, which may also be known as the electromagnetic transfer function of the haptic transducer. In an ideal case, magnetic force factor Bl can be given by the product B·l, where B is magnetic flux density and l is a total length of electrical conductor within a magnetic field. Both magnetic flux density B and length l should remain constant in an ideal case with motion occurring along a single axis.

As described above, when a current is passed through the coil of the electromagnet, the electromagnet may experience a force due to the interaction of the electromagnet and a permanent magnet. A vibrational actuator 103 may be mechanically mounted to the structure of device 100 in such a way that the vibrations due to the moving mass are transferred to the device so it can be felt by a user. In most portable electronic devices, vibrational actuator 103 is driven from a low output impedance amplifier 102 with a voltage waveform. However, a user may experience a haptic event due to the acceleration of a mass in vibrational actuator 103, working against the mass of the rest of device 100, as well as the user's hand. For a given voltage waveform applied, different vibrational actuators 103 in different devices 100 may experience different acceleration waveforms. This acceleration may depend on many variables: the resonant frequency of vibrational actuator 103; the mass value and spring designs of vibrational actuator 103; the direction of travel of the mass within vibrational actuator 103 relative to device 100 (X, Y or Z-axis); as well as how vibrational actuator 103 is mounted to device 100. The acceleration may also vary based on the total mass of device 100 and a location of vibrational actuator 103 relative to other items with significant mass within device 100.

A further problem is that vibrational actuators may have manufacturing tolerances that cause their haptic response to vary from unit to unit and also vary with temperature and other environmental conditions.

A desired haptic event may be designed by various methods. Such haptic event may then be processed offline to compute a voltage waveform that generates the desired haptic event when that voltage waveform is applied to vibrational actuator 103 in device 100. Such processed waveform may be stored in device 100.

However, such offline (or open loop) pre-processing of the intended waveform may have limitations. The waveform may be designed for a typical version of the device 100, and variations of device 100 (e g , manufacturing variations of the same model of device 100, variations between models and/or manufacturers of model 100, etc.) and the vibrational actuator 103 may cause the haptic event to be felt differently across multiple units of device 100. Additionally, a single device 100 may not reproduce the desired haptic event if the temperature (or other parameter) of the device changes from the temperature (or such other parameter) when the waveform was designed.

SUMMARY

In accordance with the teachings of the present disclosure, the disadvantages and problems associated with existing approaches for generating a haptic waveform for an electromagnetic transducer may be reduced or eliminated.

In accordance with embodiments of the present disclosure, a system may include an electromagnetic load capable of generating a haptic event and a haptic processor configured to receive at least one first parameter indicative of a desired perception of the haptic event to a user of a device comprising the electromagnetic load, receive at least one second parameter indicative of one or more characteristics of the device, and process the at least one first parameter and the at least one second parameter to generate a driving signal to the electromagnetic load in order to produce the desired perception to the user despite variances in the device that cause an actual perception of the haptic event to vary from the desired perception.

In accordance with embodiments of the present disclosure, a method may include receiving at least one first parameter indicative of a desired perception of a haptic event to a user of a device comprising an electromagnetic load capable of generating the haptic event, receiving at least one second parameter indicative of one or more characteristics of the device, and processing the at least one first parameter and the at least one second parameter to generate a driving signal to the electromagnetic load in order to produce the desired perception to the user despite variances in the device that cause an actual perception of the haptic event to vary from the desired perception.

Technical advantages of the present disclosure may be readily apparent to one having ordinary skill in the art from the figures, description and claims included herein. The objects and advantages of the embodiments will be realized and achieved at least by the elements, features, and combinations particularly pointed out in the claims.

It is to be understood that both the foregoing general description and the following detailed description are examples and explanatory and are not restrictive of the claims set forth in this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present embodiments and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings, in which like reference numbers indicate like features, and wherein:

FIG. 1 illustrates an example of a vibro-haptic system in a device, as is known in the art;

FIG. 2 illustrates an example of a Linear Resonant Actuator (LRA) modelled as a linear system, as is known in the art;

FIG. 3 illustrates selected components of an example host device, in accordance with embodiments of the present disclosure; and

FIG. 4 illustrates a flow chart of an example method for reproducing a haptic waveform at an electromagnetic transducer, in accordance with embodiments of the present disclosure.

DETAILED DESCRIPTION

The description below sets forth example embodiments according to this disclosure. Further example embodiments and implementations will be apparent to those having ordinary skill in the art. Further, those having ordinary skill in the art will recognize that various equivalent techniques may be applied in lieu of, or in conjunction with, the embodiment discussed below, and all such equivalents should be deemed as being encompassed by the present disclosure.

Various electronic devices or smart devices may have transducers, speakers, and acoustic output transducers, for example any transducer for converting a suitable electrical driving signal into an acoustic output such as a sonic pressure wave or mechanical vibration. For example, many electronic devices may include one or more speakers or loudspeakers for sound generation, for example, for playback of audio content, voice communications and/or for providing audible notifications.

Such speakers or loudspeakers may comprise an electromagnetic actuator, for example a voice coil motor, which is mechanically coupled to a flexible diaphragm, for example a conventional loudspeaker cone, or which is mechanically coupled to a surface of a device, for example the glass screen of a mobile device. Some electronic devices may also include acoustic output transducers capable of generating ultrasonic waves, for example for use in proximity detection-type applications and/or machine-to-machine communication.

Many electronic devices may additionally or alternatively include more specialized acoustic output transducers, for example, haptic transducers, tailored for generating vibrations for haptic control feedback or notifications to a user. Additionally or alternatively, an electronic device may have a connector, e.g., a socket, for making a removable mating connection with a corresponding connector of an accessory apparatus, and may be arranged to provide a driving signal to the connector so as to drive a transducer, of one or more of the types mentioned above, of the accessory apparatus when connected. Such an electronic device will thus comprise driving circuitry for driving the transducer of the host device or connected accessory with a suitable driving signal. For acoustic or haptic transducers, the driving signal may generally be an analog time varying voltage signal, for example, a time varying waveform.

FIG. 3 illustrates selected components of an example host device 300 incorporating force sensing using an electromagnetic load 301 of host device 300, in accordance with embodiments of the present disclosure. Host device 300 may include, without limitation, a mobile device, home application, vehicle, and/or any other system, device, or apparatus that includes a human-machine interface. Electromagnetic load 301 may include any suitable load with a complex impedance, including without limitation a haptic transducer, a loudspeaker, a microspeaker, a piezoelectric transducer, or other suitable transducer.

In operation, a signal generator 324 of a processing subsystem 305 of host device 300 may generate a raw transducer driving signal x′(t) (which, in some embodiments, may be a waveform signal, such as a haptic waveform signal or audio signal). Raw transducer driving signal x′(t) may be generated based on a desired playback waveform received by signal generator 324.

Raw transducer driving signal x′(t) may be received by waveform preprocessor 326 which, as described in greater detail below, may optimize raw transducer driving signal x′(t) based on an estimated back-electromotive force (EMF) voltage V_(B)(t) in order to generate processed transducer driving signal x(t) to account for variations in production tolerance, operating conditions, design differences of electromagnetic load 301, temperature, and/or other parameters in order to attempt to create a uniform perception (e.g., force or acceleration event) across host devices 300 or platforms (e.g., overcoming production variations in electromagnetic load 301 and haptics subsystems) and even different device 100 and platform designs.

Processed transducer driving signal x(t) may in turn be amplified by amplifier 306 to generate a driving signal V(t) for driving electromagnetic load 301. Responsive to driving signal V(t), a sensed terminal voltage V_(T)(t) of electromagnetic load 301 may be sensed by a terminal voltage sensing block 307, for example a volt-meter, and converted to a digital representation by a first analog-to-digital converter (ADC) 303. Similarly, sensed current I(t) may be converted to a digital representation by a second ADC 304. Current I(t) may be sensed across a shunt resistor 302 having resistance R_(s) coupled to a terminal of electromagnetic load 301.

As shown in FIG. 3, processing subsystem 305 may include a back-EMF estimate block 308 that may estimate back-EMF voltage V_(B)(t). In general, back EMF voltage V_(B)(t) may not be directly measured from outside of the haptic transducer. However, the terminal voltage V_(T)(t) measured at the terminals of the haptic transducer may be related to V_(B)(t) by:

$\begin{matrix} {{V_{T}(t)} = {{V_{B}(t)} + {{Re} \cdot {I(t)}} + {{Le} \cdot \frac{{dI}(t)}{\;{d\; t}}}}} & (2) \end{matrix}$ where the parameters are defined as described with reference to FIG. 2. Consequently, back-EMF voltage V_(B)(t) may be estimated according to equation (2) which may be rearranged as:

$\begin{matrix} {{V_{B}(t)} = {{V_{T}(t)} - {{Re} \cdot {I(t)}} - {{Le}\frac{{dI}(t)}{dt}}}} & (3) \end{matrix}$ Because back-EMF voltage V_(B)(t) may be proportional to velocity of the moving mass of electromagnetic load 301, back-EMF voltage V_(B)(t) may in turn provide an estimate of such velocity. Thus, back-EMF voltage V_(B)(t) may be estimated based on an equivalent electrical model of electromagnetic load 301, and such electrical model may vary on parameters of electromagnetic load 301 and host device 300 including resonant frequency and quality factor.

In some embodiments, back-EMF estimate block 308 may be implemented as a digital filter with a proportional and parallel difference path. The estimates of DC resistance Re and inductance Le may not need to be accurate (e.g., within an approximate 10% error may be acceptable), and thus, fixed values from an offline calibration or from a data sheet specification may be sufficient. As an example, in some embodiments, back-EMF estimate block 308 may determine estimated back-EMF voltage V_(B)(t) in accordance with the teachings of U.S. patent application Ser. No. 16/559,238, filed Sep. 3, 2019, which is incorporated by reference herein in its entirety.

The relationship among estimated back-EMF voltage V_(B)(t), magnetic force factor Bl, and an estimated velocity u(t) of a moving mass of electromagnetic load 301 may be determined from the relationship: V _(B)(t)=Bl·u(t)

Further, a force experienced by a user of host device 300 as a result of a haptic event may be proportional to an acceleration of the moving mass of electromagnetic load 301, and because acceleration is a mathematical derivative with respect to time of velocity, acceleration resulting from a haptic event of electromagnetic load 301 may be approximately proportional to the mathematical derivative with respect to time of estimated back-EMF voltage V_(B)(t).

Accordingly, waveform preprocessor 326 may (e.g., during usage of host device 300, power-up of host device 300, and/or production of host device 300) receive a signal indicative of estimated back-EMF voltage V_(B)(t) and from such signals, determine an approximate acceleration of the moving mass of electromagnetic load 301. Once such approximate acceleration is known, waveform preprocessor 326 may be configured to compare such actual approximate acceleration to raw transducer driving signal x′(t), which may be indicative of a desired acceleration profile for electromagnetic load 301, and generate processed transducer driving signal x(t) from raw transducer driving signal x′(t) based on the actual approximate acceleration to account for variations in production tolerance, operating conditions, design differences of electromagnetic load 301, temperature, and/or other parameters in order to attempt to create a uniform perception (e.g., force or acceleration event) across host devices 300 or platforms (e.g., overcoming production variations in electromagnetic load 301 and haptics subsystems) and even different device 100 and platform designs. To generate processed transducer driving signal x(t) from raw transducer driving signal x′(t), waveform preprocessor 326 may modify raw transducer driving signal x′(t) in any suitable manner (e.g., by applying appropriate gains and/or filter responses).

FIG. 4 illustrates a flow chart of an example method for reproducing a haptic waveform at electromagnetic load 301, in accordance with embodiments of the present disclosure. According to some embodiments, method 400 may begin at step 402. As noted above, teachings of the present disclosure may be implemented in a variety of configurations of host device 300. As such, the preferred initialization point for method 400 and the order of the steps comprising method 400 may depend on the implementation chosen.

At step 402, back-EMF estimate block 308 may receive signals indicative of sensed terminal voltage V_(T)(t) and sensed current I(t) associated with electromagnetic load 301. At step 404, based on sensed terminal voltage V_(T)(t) and sensed current I(t), back-EMF estimate block 308 may generate a signal indicative of estimated back-EMF voltage V_(B)(t). At step 406, waveform preprocessor 326 may determine an approximate acceleration of the moving mass of electromagnetic load 301 based on estimated back-EMF voltage V_(B)(t). At step 408, waveform preprocessor 326 may process raw transducer driving signal x′(t) based on estimated back-EMF voltage V_(B)(t) in order to generate processed transducer driving signal x(t) in order to reproduce a desired acceleration profile for electromagnetic load 301 as indicated by raw transducer driving signal x′(t) despite physical or other variances of electromagnetic load 301 and/or host device 300 that may cause such acceleration of electromagnetic load 301 to vary from the desired acceleration profile. After completion of step 408, method 400 may proceed again to step 402.

Although FIG. 4 discloses a particular number of steps to be taken with respect to method 400, method 400 may be executed with greater or fewer steps than those depicted in FIG. 4. In addition, although FIG. 4 discloses a certain order of steps to be taken with respect to method 400, the steps comprising method 400 may be completed in any suitable order.

Method 400 may be implemented in whole or part using host device 300 and/or any other system operable to implement method 400. In certain embodiments, method 400 may be implemented partially or fully in software and/or firmware embodied in computer-readable media.

In some embodiments, waveform preprocessor 326 may modify raw transducer driving signal x′(t) to generate processed transducer driving signal x(t) based on instantaneous haptic events and/or previous haptic events (e.g., sensed terminal voltage V_(T)(t), sensed current I(t), estimated back-EMF voltage V_(B)(t), DC resistance Re, and inductance Le), thus allowing for learning and adaptation of a response of waveform preprocessor 326.

As used herein, when two or more elements are referred to as “coupled” to one another, such term indicates that such two or more elements are in electronic communication or mechanical communication, as applicable, whether connected indirectly or directly, with or without intervening elements.

This disclosure encompasses all changes, substitutions, variations, alterations, and modifications to the example embodiments herein that a person having ordinary skill in the art would comprehend. Similarly, where appropriate, the appended claims encompass all changes, substitutions, variations, alterations, and modifications to the example embodiments herein that a person having ordinary skill in the art would comprehend. Moreover, reference in the appended claims to an apparatus or system or a component of an apparatus or system being adapted to, arranged to, capable of, configured to, enabled to, operable to, or operative to perform a particular function encompasses that apparatus, system, or component, whether or not it or that particular function is activated, turned on, or unlocked, as long as that apparatus, system, or component is so adapted, arranged, capable, configured, enabled, operable, or operative. Accordingly, modifications, additions, or omissions may be made to the systems, apparatuses, and methods described herein without departing from the scope of the disclosure. For example, the components of the systems and apparatuses may be integrated or separated. Moreover, the operations of the systems and apparatuses disclosed herein may be performed by more, fewer, or other components and the methods described may include more, fewer, or other steps. Additionally, steps may be performed in any suitable order. As used in this document, “each” refers to each member of a set or each member of a subset of a set.

Although exemplary embodiments are illustrated in the figures and described below, the principles of the present disclosure may be implemented using any number of techniques, whether currently known or not. The present disclosure should in no way be limited to the exemplary implementations and techniques illustrated in the drawings and described above.

Unless otherwise specifically noted, articles depicted in the drawings are not necessarily drawn to scale.

All examples and conditional language recited herein are intended for pedagogical objects to aid the reader in understanding the disclosure and the concepts contributed by the inventor to furthering the art, and are construed as being without limitation to such specifically recited examples and conditions. Although embodiments of the present disclosure have been described in detail, it should be understood that various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the disclosure.

Although specific advantages have been enumerated above, various embodiments may include some, none, or all of the enumerated advantages. Additionally, other technical advantages may become readily apparent to one of ordinary skill in the art after review of the foregoing figures and description.

To aid the Patent Office and any readers of any patent issued on this application in interpreting the claims appended hereto, applicants wish to note that they do not intend any of the appended claims or claim elements to invoke 35 U.S.C. § 112(f) unless the words “means for” or “step for” are explicitly used in the particular claim. 

What is claimed is:
 1. A system comprising: an electromagnetic load capable of generating a haptic event; a haptic processor configured to: receive at least one first parameter indicative of a desired perception of the haptic event to a user of a device comprising the electromagnetic load, further wherein the at least one first parameter is indicative of a desired acceleration of the device: receive at least one second parameter indicative of one or more characteristics of the device; and process the at least one first parameter and the at least one second parameter to generate a driving signal to the electromagnetic load in order to produce the desired perception to the user despite variances in the device that cause an actual perception of the haptic event to vary from the desired perception; and a waveform generator configured to generate a driving waveform based on the desired acceleration.
 2. The system of claim 1, wherein generating the driving signal comprises generating the driving signal by modifying the driving waveform based on the at least one second parameter.
 3. The system of claim 1, wherein the at least one second parameter is indicative of an equivalent electrical model of the electromagnetic load.
 4. The system of claim 1, wherein the at least one second parameter is indicative of at least one among a resonant frequency and quality factor of the electromagnetic load.
 5. The system of claim 1, wherein the at least one second parameter is indicative of a back-electromotive force associated with the electromagnetic load.
 6. The system of claim 1, wherein the at least one second parameter is indicative of a current haptic event and a historical haptic event associated with the device.
 7. The system of claim 1, wherein the at least one second parameter is determined during at least one among usage of the device by the user, power-up of the device, and production of the device.
 8. The system of claim 1, wherein the electromagnetic load comprises a haptic transducer.
 9. A method comprising: receiving at least one first parameter indicative of a desired perception of a haptic event to a user of a device comprising an electromagnetic load capable of generating the haptic event, further wherein the at least one first parameter is indicative of a desired acceleration of the device; receiving at least one second parameter indicative of one or more characteristics of the device; processing the at least one first parameter and the at least one second parameter to generate a driving signal to the electromagnetic load in order to produce the desired perception to the user despite variances in the device that cause an actual perception of the haptic event to vary from the desired perception; and generating a driving waveform based on the desired acceleration.
 10. The method of claim 9, wherein generating the driving signal comprises generating the driving signal by modifying the driving waveform based on the at least one second parameter.
 11. The method of claim 9, wherein the at least one second parameter is indicative of an equivalent electrical model of the electromagnetic load.
 12. The method of claim 9, wherein the at least one second parameter is indicative of at least one among a resonant frequency and quality factor of the electromagnetic load.
 13. The method of claim 9, wherein the at least one second parameter is indicative of a back-electromotive force associated with the electromagnetic load.
 14. The method of claim 9, wherein the at least one second parameter is indicative of a current haptic event and a historical haptic event associated with the device.
 15. The method of claim 9, wherein the at least one second parameter is determined during at least one among usage of the device by the user, power-up of the device, and production of the device.
 16. The method of claim 9, wherein the electromagnetic load comprises a haptic transducer. 